Edgar, You have not yet answered what I consider to be the most important question concerning this example:
How old is Sam when Pam arrives at Proxima Centauri? Sam says 5, Pam says 1.8, some alien might say 4. Is there a definite answer to this question according to P-time? Is one of the right and the others wrong? Jason On Thu, Jan 2, 2014 at 1:57 PM, Edgar L. Owen <[email protected]> wrote: > Jason, > > No, your graph is incorrect. As I said it's the horizontal grid lines of > the graph paper itself that represent present time. Where those intersect > the two world lines represents the shared present moment P-time... The > lines are NOT slanted like you have them... > > Edgar > > > > > On Thursday, January 2, 2014 1:45:21 PM UTC-5, Jason wrote: > >> >> >> >> On Thu, Jan 2, 2014 at 1:01 PM, Edgar L. Owen <[email protected]> wrote: >> >>> Jason, >>> >>> Taking your points in order. >>> >>> No contradiction. Sam and Pam do experience 10 and 6 years of clock time >>> respectively, but it's all experienced in a common present moment which >>> doesn't have a separate measurable t value of its own. Only clock time has >>> measurable t values, but they all occur in the present moment. This is a >>> direct consequence of what we started out with, that clock time t values >>> vary differently, but always in the same present momemt. No contradiction. >>> that's just the way things work. >>> >>> No, present moment time is NOT equivalent to the lengths of the paths >>> traced by each twin through spacetime. Imagine the paths are drawn on graph >>> paper, Sam's points directly above one another and Pam's in a curve off to >>> the side from Sam's start point to Sam's end point. Present moment time is >>> simply the horizontal lines on the graph paper that connect the two world >>> lines. There is always a horizontal graph paper line that connects both >>> world lines so there is always a shared present moment but the clock time t >>> values are different for those intersections. >>> >> >> >> [image: Inline image 1] >> >> That is not quite true. If Pam's path curves off to the side, then >> horizontal lines stop reaching Pam after Sam's sixth year. >> >> If, however, you connect points (which I have done with black lines) that >> correspond to equal coordinate times (that is, where the total length of >> the blue and pink lines traced out is the same) then you get the versions >> of Sam and Pam that can interact with one another. >> >> If you consider things from Pam's reference frame, then the horizontal >> lines you proposed would be different than if you considered the situation >> from Sam's reference frame. >> >> >>> >>> Again, the only way to compare differing clock time values is with >>> respect to the common present moment represented by the horizontal graph >>> paper lines which both twins exist in when they compare. That is the only >>> way a comparison is even possible. >>> >>> >> Are you saying it is impossible to say how old Sam is when Pam gets to >> Proxima Centauri? If so, then I agree. However if it is impossible to >> give a definite agree for Sam when Pam gets there, it seems that rules out >> the notion of a common present. >> >> >> >> >>> I'm not sure I'm clear by what you mean by "coordinate time" and how it >>> differs from my 'clock time'. Aren't they the same? >>> >> >> No, clock time is proper time, the "y-axis" in the above graph. >> Coordinate time, however, is the clock time of each individual's rest >> frame. In other words, what they consider their proper time to be. It is >> equal in the above graph where the lengths of the blue and pink lines are >> equal. That is, when Sam is 1 year old, both he and Pam have gone one light >> year through space-time, and likewise, when Pam is 1 year old, she >> considers both her and Sam to have traveled one light year through space >> time. In both of these instances, the coordinate time is equal. >> >> >>> Assuming so then in your last paragraphs you are once again doing an >>> entirely correct analysis of clock time variations which I accept >>> completely but which does not describe Present moment P-time. >>> >>> You have to stop trying to measure and analyze Present moment time by >>> clock time arguments. It doesn't work because they are two completely >>> separate kinds of time. Present moment time is measured not by clock time t >>> values but by the fact two observers exist in the same present moment and >>> thus are able to shake hands and compare (differing clock time t values). >>> >> >> I have no problem with explaining how both of them can shake hands, but >> your theory of P-time seems to have a problem with answering how old Sam is >> when Pam gets to Proxima centauri. This must have an objective definite >> answer if there is a common objective present, but it has no definite >> answer unless an inertial reference frame is given (or assumed). >> >> If you assume some inertial reference frame, then that is fine. You can >> say there is one unique present, but what is the motivation to give this >> inertial frame some privilege over the others? How do we decide what >> absolute rest is? >> >> Jason >> >> >>> >>> I think you may suspect I'm on to something here, and I think you may be >>> getting close to getting it. It's really quite a simple obvious concept. >>> You just have to put aside the old paradigm of a single kind of time and >>> think it through. >>> >>> Edgar >>> >>> >>> >>> >>> >>> On Thursday, January 2, 2014 12:32:19 PM UTC-5, Jason wrote: >>> >>>> >>>> >>>> >>>> On Thu, Jan 2, 2014 at 11:54 AM, Edgar L. Owen <[email protected]> wrote: >>>> >>>>> Jason, >>>>> >>>>> Sorry, but you didn't address the argument I presented. I don't see >>>>> how I can make it any clearer. Please, I respectfully ask you to reread it >>>>> and think it through. >>>>> >>>>> >>>>> And there are only 2 frames under consideration in our example. >>>>> >>>> >>>> Okay, let's use a concrete example from here on, because I think it >>>> will help: >>>> >>>> Two twins, Sam and Pam are born on the same day in the year 2000. Sam >>>> remains on Earth, and Pam goes to Proxima Centauri (4 light years away) at >>>> 80% the speed of light and then comes back at the same speed. When the >>>> twins are reunited in 2010, Sam is 10 years old and Pam is 6 years old. >>>> >>>> I think you are asking me to consider the two frames of each twin. I >>>> agree that every moment between when Pam and Sam are separated, until they >>>> are reunited, each twin exists and is doing something, and this is >>>> necessary the case in all possible frames from all possible external >>>> observers too, since they eventually meet up again. >>>> >>>> However, to me there is already one apparent contradiction in the idea >>>> of a common present when considering this example. Sam experiences 10 years >>>> of time, 10 years of biological ageing and 10 years of memories, yet Pam >>>> only experiences 6. If there is a common present, how can Sam "experience >>>> more of them" than Pam? It seems Pam only experiences 60% of the present >>>> moments that Sam does. How do you account for this with P-time? >>>> >>>> >>>>> Forget about all others. Second you are again trying to analyze >>>>> present moment time with SR. It won't work for reasons I've repeatedly >>>>> explained. >>>>> >>>>> 4 dimensionalism (SR and GR work great - for clock time, not for >>>>> Present moment time which you've already agreed is a whole different kind >>>>> of time)... >>>>> >>>> >>>> "Present moment time" in the twin example is equivalent to the lengths >>>> of the paths traced by each twin through space time. Pam's journey toward >>>> proxima centauri is the hypotenuse of a 3-4-5 triangle. She moves 4 light >>>> years through space, and 3 through proper time (she is 3 when she gets to >>>> the destination), but the path through space time is the hypotenuse, which >>>> is 5 light years long. Meanwhile, 5 years have transpired on Earth and Sam >>>> is 5 years old. >>>> >>>> During Pam's return voyage, each twin traces out another 5 light years >>>> through space time. So when the twins are reunited, in 2010, Sam's >>>> coordinate time is sqrt(0^2 + 10^2) (going 0 ly through space and 10 >>>> through proper time), and Pam's coordinate time is sqrt(8^2 + 6^2), having >>>> gone a total of 8 ly through space and 6 through proper time. Since things >>>> only interact when their x,y,z, and (coordinate time) t are the same, the >>>> 10 year old Sam who shakes hands with Pam is shaking hands with the >>>> 6-year-old Pam, since they both have a coordinate time of 10 light years. >>>> >>>> >>>>> In the common present moment someone is either actually dead or not >>>>> dead. It is true that it's not alway possible to measure when this >>>>> happened >>>>> in any particular clock time frame. But that is just trying to assign a t >>>>> value to the time of death. Nevertheless someone is always either dead or >>>>> not dead in the actual shared present moment.... >>>>> >>>> >>>> You can say the common universal present is all things that have the >>>> same coordinate time t, but only in the context of a particular inertial >>>> frame. The moment you allow different intertial frames, there can be no >>>> agreement on what the current coordinate time is for different things that >>>> are in different locations. >>>> >>>> Consider Pam's perspective during her trip from Earth to Proxima >>>> Centauri. She might consider herself to be at rest, and Earth, Sam and >>>> Proxima Centauri to be flying through the universe at 80% c. Since these >>>> things are moving so fast, she measures the distance between Earth and >>>> Proxima centauri to be length contracted to 60% of what Sam believes it to >>>> be. She thinks it is 2.4 ly, not 4 ly. Therefore, at Proxima Centauri's >>>> present speed it will take 3 years to get to her (2.4 / 0.8). By the time >>>> Proxima Centauri arrives, she believes her coordinate time is only 3 light >>>> years (as is Sam's from her perspective), she thinks Sam is only (3 * 60%) >>>> = 1.8 years old, while Sam thinks he is 5 by the time she gets to Proxima >>>> centauri. How does your notion of a common present address this? >>>> >>>> How can Sam believe he is 5, while Pam believes he is 1.8 (when Pam >>>> arrives at her destination). Note both twins agree that Pam is 3 at the >>>> time she arrives at Proxima Centauri, and both twins agree that when they >>>> meet at Earth in 2010 that Sam is 10 and that Pam is 6. >>>> >>>> This shows you can't extrapolate from common agreements when two people >>>> are together to common agreements when two people are apart, just because >>>> there is agreement when they meet up again. >>>> >>>> Jason >>>> >>>> >>>> >>>>> >>>>> >>>>> On Thursday, January 2, 2014 9:56:44 AM UTC-5, Jason wrote: >>>>> >>>>>> >>>>>> >>>>>> >>>>>> On Thu, Jan 2, 2014 at 8:50 AM, Edgar L. Owen <[email protected]>wrote: >>>>>> >>>>>>> Hi Jason, >>>>>>> >>>>>>> No, sadly you haven't quite gotten it yet but you are getting closer >>>>>>> it seems. >>>>>>> >>>>>>> First the twins do NOT have the same (x,y,z,t) coordinate times >>>>>>> (that would be true of an SR constant velocity example, but not the >>>>>>> twins' >>>>>>> GR acceleration based example). Their watches show they don't, and when >>>>>>> they compare watches both twins agree with the readings on both watches. >>>>>>> Not only do the twins have different ages but their clocks accurate show >>>>>>> that age difference. Both twins agree that the traveling twin aged less >>>>>>> because comparing their clocks both mechanical and biological confirms >>>>>>> that. >>>>>>> >>>>>>> Thus they have different (x,y,z,t) coordinates yet they DO interact. >>>>>>> Why? Only because they share the exact same present moment which is the >>>>>>> only place interactions can occur whether clock times are the same or >>>>>>> not. >>>>>>> And that present moment P-time is a completely independent kind of time >>>>>>> from clock time. There is simply no way around this. >>>>>>> >>>>>>> >>>>>> You are describing coordinate time. >>>>>> >>>>>> >>>>>>> Yes, you are correct the twins shaking hands and comparing watches >>>>>>> confirms a shared present moment by direct experiment if the (x,y,z) >>>>>>> coordinates are the same but not they they different. However the >>>>>>> argument >>>>>>> to deduce a common present moment when (x,y,z) coordinates are >>>>>>> different is >>>>>>> simple and clear. I've already posted it a couple of times but will >>>>>>> summarize it again. >>>>>>> >>>>>>> The twins start and end at the same (x,y,z) coordinates. At both >>>>>>> times we agree they share the same present moment. Their passages from >>>>>>> point A to point B must both be represented by continuous lines, one >>>>>>> curved, one straight. During every point during that passage both twins >>>>>>> continuously experience their own present moment time without >>>>>>> interruption >>>>>>> and those present times are the same when they start and when they meet >>>>>>> up >>>>>>> again. Thus we must logically conclude that at every present time moment >>>>>>> for either observer there absolutely must have been a corresponding >>>>>>> present >>>>>>> time moment for the other. >>>>>>> >>>>>> >>>>>> You have demonstrated it for two observers at the same x,y,z, but it >>>>>> does not logically follow for different x,y,z's. >>>>>> >>>>>> >>>>>>> This is not directly observable >>>>>>> >>>>>> >>>>>> So we should maintain some doubt.. >>>>>> >>>>>> >>>>>>> but is the only logical conclusion >>>>>>> >>>>>> >>>>>> SR shows there is another possible conclusion. >>>>>> >>>>>> >>>>>>> based on their starting and ending at a shared present moment and >>>>>>> both their spacetime travels being continuous with no breaks in between. >>>>>>> >>>>>> >>>>>> This can also be explained by a an (approximately) continuous, >>>>>> four-dimensional reality, in which all events are embedded. >>>>>> >>>>>> >>>>>>> >>>>>>> The easy way to understand this is that every present moment for >>>>>>> either twin, the other twin must actually exist and be doing something >>>>>>> too. >>>>>>> >>>>>> >>>>>> In some relativistic frames, with separated twins might be considered >>>>>> dead, and the other still alive, while in another frame, the former twin >>>>>> is >>>>>> still and the other is dead. The only sense in which the other is >>>>>> guaranteed to exist and be doing something is that both twin's "world >>>>>> tubes" exist and are eternally embedded in the four dimensional reality. >>>>>> >>>>>> >>>>>>> There is absolutely no way around that! Thus they must share a >>>>>>> common present moment in which they are existing and doing something >>>>>>> even >>>>>>> when they are separated spatially. Clearly this cannot be experimentally >>>>>>> confirmed (measured) but it is the only tenable logical conclusion >>>>>>> unless >>>>>>> you think things pop in and out of existence which they don't. >>>>>>> >>>>>>> >>>>>> Now again for the nth time. don't try to analyze this by relativistic >>>>>>> clock time theory. That correctly describes how clock times change >>>>>>> during >>>>>>> the trip but has no relevance to present time whatsoever! Two completely >>>>>>> different kinds of time. >>>>>>> >>>>>> >>>>>> I fail to see how this is any different from coordinate time vs. >>>>>> proper time in SR. >>>>>> >>>>>> >>>>>>> >>>>>>> Thus the only possible conclusion is that there is a common >>>>>>> universal shared present moment time which is completely different from >>>>>>> clock time. >>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>>> Why doesn't four dimensionalism work? >>>>>> >>>>>> Jason >>>>>> >>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Wednesday, January 1, 2014 3:15:27 PM UTC-5, Jason wrote: >>>>>>> >>>>>>>> Edgar, >>>>>>>> >>>>>>>> I believe I may understand your point about a universal present, >>>>>>>> but it is something relativity handles, as far as I can see, without >>>>>>>> having >>>>>>>> to postulate anything new. Anything having the same (x, y, z, t) >>>>>>>> coordinates can interact, where t is coordinate time. It seems like you >>>>>>>> believe that because the twins are different ages (in different proper >>>>>>>> times), that they cannot interact. But they can, because each has >>>>>>>> traced >>>>>>>> exactly 10 light years through space-time (their coordinate times are >>>>>>>> the >>>>>>>> same). >>>>>>>> >>>>>>>> So you might say everything with the same coordinate time, at the >>>>>>>> same place (x, y, z) the same, shares a present moment. But you cannot >>>>>>>> use >>>>>>>> this fact to extrapolate to spatially separated things sharing a >>>>>>>> present. >>>>>>>> For this, the definition of a present (what things exist having the >>>>>>>> same >>>>>>>> coordinate times) differs in different reference frames. >>>>>>>> >>>>>>>> Jason >>>>>>>> >>>>>>>> >>>>>>>> On Wed, Jan 1, 2014 at 3:01 PM, Jason Resch <[email protected]>wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Wed, Jan 1, 2014 at 8:41 AM, Russell Standish < >>>>>>>>> [email protected]> wrote: >>>>>>>>> >>>>>>>>>> On Mon, Dec 30, 2013 at 01:20:35AM -0800, Edgar L. Owen wrote: >>>>>>>>>> > Jason, >>>>>>>>>> > >>>>>>>>>> > That's a totally off the wall answer. When the two shake hands >>>>>>>>>> it's not >>>>>>>>>> > just photons that are interacting, it's the electrons, protons >>>>>>>>>> and neutrons >>>>>>>>>> > of the matter of their hands which don't travel at the speed of >>>>>>>>>> light. >>>>>>>>>> > >>>>>>>>>> > Goodness gracious! >>>>>>>>>> > >>>>>>>>>> > Edgar >>>>>>>>>> > >>>>>>>>>> >>>>>>>>>> Jason is correct - electron-electron and electron-proton >>>>>>>>>> interactions >>>>>>>>>> are mediated by photons. Only nucleon-nucleon interactions are >>>>>>>>>> mediated by different stuff (gluons in that case), but for all >>>>>>>>>> practical purposes, the strong force is irrelevant to the >>>>>>>>>> phenomenon >>>>>>>>>> of handshaking. >>>>>>>>>> >>>>>>>>> >>>>>>>>> And if it were, say in some particle accelerator, the gluons also >>>>>>>>> travel at the speed of light and their present is spread across all >>>>>>>>> proper >>>>>>>>> times. >>>>>>>>> >>>>>>>>> >>>>>>>>>> >>>>>>>>>> Which gets us to the more important point. You idealise a >>>>>>>>>> handshake as >>>>>>>>>> instantaneous as a demonstration of your "present moment", but in >>>>>>>>>> fact >>>>>>>>>> those interactions Jason was alluding to are smeared out over a >>>>>>>>>> temporal duration of the order of a few picoseconds (a duration >>>>>>>>>> well >>>>>>>>>> measurable by current day technology - my laptop's CPU clock >>>>>>>>>> cycles on >>>>>>>>>> a sub-picosecond timescale, for example). >>>>>>>>>> >>>>>>>>> >>>>>>>>> You must have a VERY fast laptop! :-) >>>>>>>>> >>>>>>>>> Jason >>>>>>>>> >>>>>>>>> >>>>>>>>>> This doesn't matter much for human affairs, but becomes quite >>>>>>>>>> significant when extrapolating over cosmological scales. >>>>>>>>>> >>>>>>>>>> Cheers >>>>>>>>>> -- >>>>>>>>>> >>>>>>>>>> ------------------------------------------------------------ >>>>>>>>>> ---------------- >>>>>>>>>> Prof Russell Standish Phone 0425 253119 (mobile) >>>>>>>>>> Principal, High Performance Coders >>>>>>>>>> Visiting Professor of Mathematics [email protected] >>>>>>>>>> >>>>>>>>>> University of New South Wales http://www.hpcoders.com.au >>>>>>>>>> ------------------------------------------------------------ >>>>>>>>>> ---------------- >>>>>>>>>> >>>>>>>>>> -- >>>>>>>>>> You received this message because you are subscribed to the >>>>>>>>>> Google Groups "Everything List" group. >>>>>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>>>>> send an email to [email protected]. >>>>>>>>>> To post to this group, send email to [email protected]. >>>>>>>>>> >>>>>>>>>> Visit this group at http://groups.google.com/group >>>>>>>>>> /everything-list. >>>>>>>>>> For more options, visit https://groups.google.com/groups/opt_out. >>>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>> -- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "Everything List" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>> send an email to [email protected]. >>>>>>> To post to this group, send email to [email protected]. >>>>>>> Visit this group at http://groups.google.com/group/everything-list. >>>>>>> For more options, visit https://groups.google.com/groups/opt_out. >>>>>>> >>>>>> >>>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Everything List" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to [email protected]. >>>>> To post to this group, send email to [email protected]. >>>>> Visit this group at http://groups.google.com/group/everything-list. >>>>> For more options, visit https://groups.google.com/groups/opt_out. >>>>> >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Everything List" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at http://groups.google.com/group/everything-list. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> >> -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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